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C »1 1 LEFT END OF ONE TRUSS 1 L.-•1\ ., 1-----1 J-----l 3 ''\ Cut away and discard dashed portion 1f1 Fig. 1 TRUSS CUTTING DIAGRAM These are still needed at the outer sides of each pair but are to be removed in the centers. Use a razor saw and swiss files to clean them off. All through this construction, flash (the ridges formed in the molding process) and sprues (the gates through which the plastic was poured) should be removed and the surfaces smoothed. Also, in sonne places where parts are to be butted and cemented together, you will find the so-called fiat and square edges have a slight slope, making square butting impossible. This is due to the draft that is needed in the molding process. Such sloped surfaces must be squared with a file before joining the parts. With the XX pieces now joined, you can turn to the bottom latticework. It's labeled "bottom brace" on the Atlas instruction sheet diagram. Like the sides of the bridge, one end panel should be removed from each of the four original pieces. Then they should be joined into two side-by-side pairs and finally should be joined end to end. You will have to remove some of the tongues and struts to make the parts fit. The joints won't look realistic, so cut five strips of.020" styrene scale 5" wide and 63" long. Cement these over the struts between each pair of existing gussets. Weight the assembly overnight to hold everything in position until the cement has dried. After the plastic part of the bridge is completed you can add the floor beams. Cut these from 6x8 timber 6'-9" long, with the ends notched, somewhat like tenons, so they will slip into the channels on the inner sides of the top chords as in fig. 2. Normally, the deck of a bridge con- sists of three layers of timber. Running lengthwise, directly under each rail, is a stringer. Typically, for a bridge this size, the stringer would be three pieces side by side, of perhaps 12 x 18 material. These are shown in phantom in fig. 2, but I did not include them in my model. The next layer consists of bridge ties. Mine are simply supported on the top chords instead of being on stringers. Finally come the rails, six of them. At the outside October 1973 • 1 ,\ :' \ \ 9.411 I. '1 '' '' '1 '' 1 /// 't, ''',....\ . iE,' ''3'. ./.. 'r¥.0, I . :5.:9. , 11 3 \.i: Y - j.-----1 ,- Top chord ¥ ,/ 4 Gussets ore left intact -4-__.1 L 1 /,1i '''' t// 8 : ,, i ..bri 1 6/ ...r:., Cor away ond discard dashed portion' 1-·> Gussets and post removed I T,4 / 56 . "1*f,» <fla. #WA 111'f•» . RIGHT END OF ONE TRUSS Not to scale are two wood guardrails. Then come the running rails, and inside of them, two metal guardrails: fig. 3. It is important to have the ties uniform in spacing, at right angles to the trusses, and neatly aligned along their ends. To accomplish this, it helps to make a "piano key" jig. This consists of slots into which the ties fall in perfect alignment. They are held in place until the wood guardrails are attached. I made my jig on a 15" (38-cm.) length ofplywood. Pieces of6x8 strip stock were attached to it permanently to form spacers and an alignment spine. Start with the spine. This is a 15" -long piece cemented along one edge of the plywood. Cement all of these pieces so the broad side is down. Now cut 34 pieces ofthe same material about scale 7 feet long. Attach the first at one end of the spine and be sure it is exactly at right angles to the spine. Place a tie next to it as a spacer and then attach another 7-foot "piano key." Continue, always keeping the keys at right angles to the spine, until you have formed pockets to accept all 33 ties. With the ties held in place and in align- ment, it is a simple matter to add the timber guardrails. You can also attach running rails and metal guardrails while the ties are in the jig if you wish. Paint the nut-bolt-washer castings either a weathered black or a rusty color before installing them. Slip these into .040" (1-mm.) holes. You can drill the holes with a pin vise. Add a bit of the cement to each casting before pressing it into the hole. Caution: The track spikes you select should not be so long that they pass all the way through your bridge ties. If they must, grind offthe tip from the underside. One's natural tendency is to end the rails on the truss opposite each other, but it will be far better to stagger them at least 5 scale feet, letting one or both rails extend onto the approach roadway before reaching the next rail joint. If you weather your rails, the sides of the running rails and the entire surface 1 / 1 \.. :\ !,:/ .. 1 1 Tf .11 ...':li:.: /'..>L-1-4/t I4 1 '' ,; 7-18 1 // -1 6'.9" n-I-i1 , i Floor beam - : ' :11 | • i make 16 -\ 4 lili Fig. 2 FLOOR BEAMS Running 1 -Ln11 :: 1-1 n 1-1 1-7 ninO 0 01 rails --- f-/. 8" 4 /6x8 wood guardrail I.11.l ill i.1 I.11.l ili 1.1 \ gwordroll leGW.1.1 f 0 .-ff IT-T-7- . 10 '. Grandt 1 YS" N-B-W-' Fig. 3 DECK ASSEMBLY of the metal guardrails should be coated. Final assembly is next. Follow steps A, B, and C on the Atlas instructions for cementing the various components of the truss assembly together. Now insert the 16 wood floor beams into the truss channels. These should be a sliding fit, as they may have to be shifted during assembly. Insert two above each end panel and three above each of the other panels. Place small pieces of masking tape over the top of each of the 16 floor beams as a painting mask. If your bridge will carry engines that are comparatively heavy, you may want to add a wood crossmember between each of the square gussets at each end of the truss in order to provide more load-bearing surface and strength. These two pieces will be triangular in cross section. Paint the truss assembly. I used Floquil's grimy black. Spray lightly to avoid marring the fine rivet detail. Use two or three light coats if necessary, rather than one heavy one. You may also want to paint the leftover pieces from the Atlas kits for later use as detailing scraps. They make good flatcar loads and look great scattered near a line shack as if they were spare trusses being stored for use by your B&B maintenance gang at a later date. Be sure to weather these pieces with extra amounts of rust, mud, and so forth. The deck assembly is secured to the truss superstructure by placing cement on the tops of the 16 floor beams and laying the deck over the trusses, keeping the tie overhang on each side equal. You will have to maneuver the floor beams back and forth in their slots so that each comes immediately below a track tie. I would suggest using a slow-drying cement for this because it may take some time to align everything properly. Remove any excess cement. Put a weight on the bridge and allow the joints to set overnight. Prepare some timber cribbing or stone- work abutments to support the ends of the truss and it's ready for installation and that satisfying first crossing by your favorite locomotive. 55 . 4 -Tr--' 1111 1 I I I I I 1 i lilI U UU Uu/2-1 UUI 0 lopoot Top view - i •E»·._ f - Trusses --- - --. •Optional stringers: see text